Field of the Invention
The present invention relates to infinitely variable transmission systems to be used to transmit one input of torque and speed, to two outputs with independently varying speeds and torques in forward, reverse and neutral (stop) directions, suitable to be used for differentially steered vehicles.
Description of the Related Art
Differential steering transmission systems are widely used in a range of vehicles from zero-turn lawn mowers to tracked vehicles such as skid steers, and to other vehicles such as robotic vehicles. They operate on the principle of driving the two driving components, such as tracks or wheels, referred to as tracks from here on, on both sides of the vehicle at independently varying speeds and directions. These vehicles can achieve versatile driving operations, from zero-turn, where the tracks are driven at opposing directions, to straight driving in both forward and reverse directions, in a seamless transition of gearing.
Traditionally, this behavior is achieved via use of hydraulic drive systems. The two tracks are driven by hydraulic motors, which are driven by one or more hydraulic pumps. In turn, the hydraulic pumps are driven by the engine. These hydraulic systems run on the same infinitely variable transmission principle, where the operator can hold the output shafts at neutral (stop) position, or turn in forward and reverse directions in infinitesimally incremental adjustments. In many cases, the operator may have two controls, each assigned to control the operation of each track. In the case of a hydraulic piston pump, the controls may change the swash plate angle which adjusts the direction and speed that the hydraulic fluid is delivered to the hydraulic motor, and hence the speed and direction of the rotation of each track.
Same operational behavior is also achieved by the use of electric motors, where dedicated motors drive each track. The motors can be controlled independently in terms of speed, torque and direction. Required electric power may be supplied via batteries or through an engine driven generation system.
Aforementioned systems require the engine output mechanical motion energy to be converted to other forms of energy such as electrical or hydraulic flow, then again to be converted back to mechanical motion energy at the tracks. As a result, these systems carry the burden of efficiency losses, as well as added costs, weight and durability impact.
Other differential steering systems consist of various combinations of differentials, clutches, brakes, gearboxes and hydraulic systems that are utilized more commonly in larger applications. Depending on the arrangement, these systems might have limitations in the function of infinite variability of gearing, steering, and reversibility, compared to the aforementioned hydraulic or electric motor driven systems.
The object of this invention is to create an infinitely variable transmission system that performs the aforementioned functions of hydraulic or electric motor driven systems, without the need for converting mechanical motion energy into any other forms of energy, hence providing simplicity, improved efficiency, durability, weight reduction, and costs savings.